Mark J. Estienne Virginia Tech

Resources Authored


Anestrus in Swine

Publish Date: April 9, 2010

By definition, anestrus is a condition in swine during which females do not exhibit estrous cycles. During anestrus, the ovaries are relatively inactive and neither large follicles (ovarian structures that contain an ovum or egg, and that secrete large quantities of estrogen; Figure 1) or functional corpora lutea (ovarian structures that secrete progesterone; Figure 2) are present. Anestrus usually results from insufficient secretion of gonadotropin-releasing hormone (GnRH) from the hypothalamic area of the brain. In cycling gilts and sows, GnRH travels by blood to the anterior pituitary gland, a pea-sized organ located near the base of the brain, where it causes secretion of the gonadotropins, luteinizing hormone (LH) and folliclestimulating hormone (FSH). The LH and FSH in turn, stimulate growth of ovarian follicles, ovulation and in the case of LH, normal function of corpora lutea.

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Resources Reviewed


Environmental enrichment strategies for swine

Publish Date: July 28, 2022

Environmental enrichment provides an opportunity to improve the living conditions of farm animals. Current farming systems offer little stimulation, other than food and water and animals are often closely confined in groups (with relatively little space per animal). Such environments may be inadequate to fulfil all the needs of an animal, or an animal may be unable to cope effectively. Enrichment can be used to encourage more of the natural behaviors of animals, thereby enhancing their welfare.

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Synchronization of estrus in swine

Publish Date: June 3, 2006

Production calendars for most swine farms are based upon the reproductive cycle of sows and gilts. The key reproductive event that determines when females begin their reproductive cycles is the onset of estrus. Estrus normally occurs spontaneously in gilts and mature females that are not pregnant or lactating. Once estrous cycles have begun, they normally occur every 18 to 21 days. From a production standpoint, on any given day, it is difficult to predict or control the number of females in estrus. The ability to precisely control the onset of estrus is referred to as synchronization. Effective management and pharmacological techniques for synchronization of estrus in swine are available. However, strategies that work in prepubertal gilts are not effective in mature females and vice versa.

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